By the way - the address lines tie directly into the temp sensors (LM75 I believe) so the controller can tell which board has which temperature. PLUG tells the controller a board is attached, but I forget if it pulls high or pulls low. Been a couple years since I needed to know that, but I've got notes on it at the shop. Everything else should go straight across.

Technically all you need to get hashing is 3V3, RST, RX, TX and GND. With PLUG tied to the appropriate rail.